Got this from them:
Dear traders,
Yesterday around 14.00 UTC we had liquidation algorithms of portfolio margin users creation a chaos in the 29 December future. This resulted finally in bankruptcies of more than 105 BTC. Further various client accounts had unjust losses due to liquidations as well.
We had to halt trading yesterday for a while to fix the issue before we could continue again. We are sorry for the downtime.
We solved the issue of the losses by contacting our biggest market makers and traders that have been making profits trading against the malicious algorithm at prices far above the market. We are grateful for their understanding of the incident and for their direct support of our exchange.
Further we decided to refill the insurance fund further such that all other traders will remain completely unaffected and no profits will be socialized among other traders in this session at all.
The total final loss left for the exchange amounts to around 60 BTC (or USD 235.000 at the time of writing). Please note that all users' funds are safe and we as an exchange can, of course, handle a loss of 60 BTC. The exchange will continue operating as normal.
This was our first major incident since we opened doors for trading in the summer of 2016. We will work hard now to improve various liquidation algorithms such that this could never occur again. This might further delay the launch of new products like Ethereum futures and our upcoming Spot Exchange.
The insurance fund will also be replenished again with 25 BTC.
Best regards,
Deribit Team
Johan Jansen - CEO
Marius Jansen - CMO